The overall objectives of this project are to study the immunological parameters associated with the survival of Rous sarcomas as well as normal allogeneic cells in chickens that possess demonstrable cellular immunity to the foreign tissues. A detailed analysis of the blocking activity of serum from normal, bursectomized (agammaglobulinemic) and thymectomized (T cell deficient) inbred chickens will be made in order to establish the mode of action of blocking factors or "inhibitors" and their possible role in immunological tolerance. A search for mechanisms which will abrogate the effects of such serum factors in tumor bearing animals will be made. The approach will be to study serum blocking factors in normal and agammaglobulinemic (a gamma) birds and to establish their relationship to cellular immunity and behavior of tumors in vivo, to establish immunological methods for detection of blocking factors and to determine the efficacy of immunoabsorbents to deplete serum of blocking factors. Correlative studies to be performed in allogeneic tolerance will emphasize: a) an analysis of blocking factors in a gamma birds with complete or partial tolerance, b) the effect of blocking factor depletion on skin graft survival and cellular chimerism and c) identification of effector cells.